Under the Hood
Prudence brings together many open source libraries, some of which were designed specifically for Prudence.
Consider this as Prudence's "acknowledgments" page. Hundreds of people have worked on these libraries, and we're grateful to all of them for sharing their hard work, for embracing open source licensing, and for adhering to design principles that allow reuse of their work in other projects, such as Prudence.
The JVM
How wonderful that the best-performing, most robust, secure and widely ported virtual machine is now open source? How wonderful that you can use it with JavaScript, Python, Ruby, Clojure, PHP and others languages?
We strongly recommend the JVM for enterprise and scalable Internet applications, even if you're not particularly fond of Java-the-programming-language. Treat Java, if you will, as the low machine-level language: Java is to the JVM as C is to Unix. You "drop down" to Java only if you have to do some machine-level work. Otherwise, use the higher-level languages.
Scripturian
Scripturian is Prudence's "special sauce": a small, magical library that makes sure that your code runs well on the JVM and can handle the concurrency introduced by HTTP requests and Restlet. It is developed in tandem with Prudence.
Our premise was this: to make Prudence applications easy to deploy, they could not be standard Java applications. The cycle of compilation and packaging required by Java is unnecessarily cumbersome. Although we could have implemented something like the on-the-fly Java compilation done in JSP, we felt that, if that's the route to go, many exciting choices open up besides Java, and that these languages are more relevant to Prudence's goals.
Unfortunately, we found that integrating JVM languages into Prudence was anything but trivial. Each implementation had its own idea of what integration could mean. We tried to standardize on JSR-223 (the Java scripting standard), but found that adherence to the specification was inconsistent, and that the specification itself is vague, especially when it comes to threading. We hacked and hacked and hacked. We even submitted patches to fix broken implementations of various languages. All in all, we probably spent more time on this than on any other aspect of Prudence.
The result is an API more abstract than JSR-223, but with a clear threading model. Under the hood, Scripturian contains many tricks and mechanisms to make each language work correctly and well, but you don't have to worry about any of it: Scripturian just works.
Jython, JRuby, Clojure, Rhino, Quercus, Groovy
Prudence would hardly be as exciting if you had to use Java.
These open source language engines have allowed us to extend the power of Prudence, REST and the JVM to languages outside of Java. Some of these engines are large, complex projects, and are in fact the biggest libraries included in Prudence. We strongly recommend you join in the communities surrounding the language engines corresponding to your favorite flavor of Prudence.
Restlet
Prudence went through many in-house transformations before aligning itself strongly with Restlet. First, we experimented with Facelets, but ended up giving up on JSF, its complex lifecycle, and on the promise of component-based web development in general. Then, we designed REST architectures using servlets and Succinct templates, but found it awkward to force servlets into a REST architecture. Discovering Restlet was a breath of fresh air.
Restlet's super-powers are three:
- It's a clean abstraction of HTTP requests, responses and headers over best-of-breed HTTP engines, such as Jetty, Grizzly and Netty. Automatically gain the scalable advantages of non-blocking I/O and even asynchronous request handling (which will be even better supported in Restlet 2.1). Restlet transparently handles conditional requests, content negotiation, and other complicated HTTP mechanisms.
- Powerful URI routing and manipulation. Expose your service to users and APIs with elegance and coherence. Make sure the URI reaches its destination, with support for virtual hosting, rewriting, templating, and other useful real-world features. Restlet is truly the Swiss army knife of URIs.
- Straightforward data representation and consumption through a diverse set of extensions. Expose your data using any standard format, and even convert it on the fly. Easily parse data received from clients.
Restlet is a great library, with a great ecosystem of extensions. In embracing it, though, we missed some of the advantages of having a servlet container: easy deployment and configuration, centralized logging, etc. We also missed having JSP at our fingertips to quickly push out dynamic HTML.
Prudence is meant to fill in these gaps.
Special thanks go to Noelios, and especially Jérôme Louvel, for cultivating such a vibrant community around Restlet. It's a solid foundation.
Succinct
Succinct, like Scripturian, started as a part of Prudence, and was in fact one of its earliest components. It has since branched out into an independent library. We created it because we wanted straightforward, scalable templating built in to Prudence, and were unsatisfied by other open source offerings. We think you might like it. (If not, Prudence fully supports Velocity.)
Jygments
Yet another Prudence side-project…
For Prudence's debug mode, we wanted good syntax highlighting for viewing source code. We found nothing adequate enough in the Java world, though we fell in love with Pygments. For a while, we ran Pygments in Prudence via Jython, but found it too heavy for this particular use case. Thus, Jygments was born as a port of Pygments to Java.
H2
We're great fans of this lean and mean database engine! It has allowed us to distribute Prudence with a fully-functioning data-drive demo application, without any external dependencies. We're proud to introduce H2, through Prudence, to more people, and we believe you'll find it fast enough, reliable enough, and flexible enough for many production environments.
Hazelcast
This library is a dream come true: distributed, fault-tolerant implementations of the JVM's standard collection interfaces, with distributed task queues thrown into the box. We are confident that Hazelcast will help many Prudence users scale their applications easily and elegantly.
See Prudence clusters for more information on how Hazelcast is integrated into Prudence.
